It also depends on PrC plans - and heavily, now, on wether or not your DM will allow you to use the Variant Specialist Wizard rules in Unearthed Arcana.

For examples:

Conjuration specialist, with the "rapid summons" ability (in place of having a familiar): summoning monster spells are 1 standard action (instead of 1 full round). Yes, this means you CAN Quicken them! Alternately (or as well as rapid summons), Enhanced Summons, which replaces your bonus feat progression. Augment Summons instead of scribe scroll, harder to dispel your creatures, and eventually gain another +2 or +4 to Strength and Constitution, on top of Augment Summoning.

An Evoker would get great mileage from Energy Substitution - which is basically all five such feats, chosen on-the-fly, in return for sacrificing the Wizard's bonus feat options.

An illusionist giving up their bonus feats to get Shadow Shaper (instead of bonus wizard feats), can basically fill in a bit for a second-string Rogue. Hide as a class skill, intelligence modifier AND dexterity modifier added to Hide checks, +1 to the save DC of all his illusion spells, Hide in Plain Sight (!!), and eventually, the ability to be treated as invisible when in ANY illumination conditions that would give ANY degree of concealment. Drop a darkness spell, and disappear completely ...!

A Necromancer can exchange their familiar for Skeletal Minion - basically, kind of like a specialised form of Improved Familiar, for free, at 1st level - with only one option open.

Transmuters can, with Spell Versatility - which costs them their bonus feat progression - gain one spell per five levels which they can treat as a Transmutation spell ... even if it is normally from an opposed school! Further, Transmutable Memory can be VERY powerful, despite costing them their extra prepared Transmutation spell per spell level: it lets them un-prepare as many spells as they like (once per day), and replace them with an identical number of spell levels of newly-prepared spells (the process takes 1 minute per spell level given up). This even allows, per the example, to give up two 1st level spells and two 2d level spells ... for two third level spells! IOW, you can trade in all those low level spells, for more HIGH-level spells!

So, I dunno; a Conjuror with Rapid and Enhanced Summons ... or a Transmuter with Spell Versatility and Transmutable Memory. Well ... I'd be interested in giving either of THOSE a try, in the right campaign!

And Evokers with Energy Substitution stop having to worry about which element(s) to prepare spells of each day; if he's loaded out with fireballs, and the party encounters some fire elementals ... *poof* instant "Coldball" ...! Always use the element a creature is susceptible to, without needing any advanced warning? That's nice, indeed!

I have yet to see a wizard that didn't have one divination per level, even blaster mages.

So, the net result is, you are getting one more slot, for either one school banned, or two schools banned.

I think that I would specialize in Dviniation, and be a better blaster mage than an evoker, because we both would have a free spell slot, both of us would have one divination per level, except I paid half price.

There is no reason to NOT specialize in divination if you are going to specialize, everyone with sense prepares divination spells, at least one per level.

Now, if you are not going to specialize at all, then I suggest that you don't specialize in divination.